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I'd like to know if these are all direct substitutes (at least within safe operating specs):
6L6
5881
KT66
7581
WE 350Any recommendations? Thanks.
Follow Ups:
Hi,There are two things to consider with these tubes, max voltage specs and filament current specs. On the the first subject, the 6L6 types can be broken down into the 6L6, the 6L6B (5881 and I think the 350B), and the 6L6C (7581, KT-66). You should check out the max plate volts for each type as your circuit may not be suitable for all of them. The 350B and KT-66 both draw appreciably more heater current than the other types listed (1.3 and 1.6 amps or so versus 0.9 amps for the other types, if I recall corectly). Again, your power transformer may or may not be able to handle the current requirements.
For sound, well, to each his own. In the circuits I have tried (single ended and push-pull), running them in tetrode, the 350B is the most even handed of the type. Nice and smooth across all frequencies, nice midrange, great tube. The KT-66 has a warmer tone with less definition at the frequency extremes, but nice mid range. Some 6L6G's (particularly RCA, Sylvania, TungSol) sound pretty good. Nice definition at the frequency extremes, but a little midrang drop out. As for 5881's, they are nothing special in tetrode. However, when run in triode mode they sound pretty good (I should note that I was using them outside the rated screen voltage, about 20% above max. Tough tube.)
Hope this helps,
Rodney
in the strictest sense they are not subs for each other because some have a lot higher plate voltage rating than some of the others. But other than that they have the same pin out, and **probably** can be subed for each other, except that the 6L6 (metal) sometimes has pin one connected internally to another element within the tube and can cause problems if the amp it is put in has something connected to pin one of the tube socket. ron
GF,One simple Q. What tone are you after? Strong bass? Clean highs? Smooth midrange?
Each tube type (and specific manufacturer) has its own forte and weaknesses.
Sorry, for the side-track Q---but it will help you decide the power tube/speaker combo. Also, the kind of music you like is important.
Thanks Steve. I like all sorts of music and dont mind buying a couple of types to tube roll, depending on what i'm listening to. I'd like to make sure they are all compatible in the preamp though. I wouldn't want to burn my pre :)Can you give me a general idea of what each type sounds like?
GF,
If I had one choice, I'd pick the silver-gold labeled "stylized S" logo, St Petersburg made Svetlana 6L6GC..... whew!!!These were made in the 1990's. Need more bottom end balls? The Philips 7581A. Rebiasing is needed, as when inserting any new power tube.
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